JPS61126791A - Manufacture of surface heat generating body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Technical field of invention) The present invention relates to a method for manufacturing a planar heating element.

(Technical Background of the Invention and Key Points) Conventional planar heating elements generally use a plastic substrate. Conductive material?
Print or nichrome wire? It is pasted together and a plastic sheet is placed on top to create a sandwich structure. This sheet heating element made of plastic is flexible, highly workable, can be made into a large area, and is inexpensive, but it can be used at temperatures below the serviceable temperature of plastic.

The disadvantage is that it can usually only be heated to about 700℃, and cannot be heated to high temperatures. Another disadvantage is that rapid heating is not possible due to the limited heat resistance temperature.

The other method is to create a printed sheet of ceramics from the raw materials mentioned above, coat it with a heating element such as a conductor or a resistor, or apply a mark I11 on it, and then assemble it. In this case, Ceramics are fired @ degree is 1.300 ~
Since the temperature is 1.800 C, conductive pastes and resistive pastes that can withstand this temperature are required, but there are none that can be fired in an oxidizing atmosphere. The paste that can be used is Au
, PD, Pt, Mo, and W, which also have the difficulty of firing in a reducing atmosphere. This makes costs very high.

In addition, when an alumina substrate is used, the thermal expansion coefficient of alumina is 60 to 70 x 10-' 1/[,
It also has the disadvantage of being vulnerable to thermal shock.

Also, tortoise-resistant paste on the ceramic green sheet? The heating element obtained by printing and firing at a low temperature of 700 to 900C has pores left on the surface of the substrate due to incomplete sintering of the substrate, and the resistor base permeates into the pores when electricity is applied.
The drawback was that a constant resistance value could not be obtained.

In addition, in the conventional Atsuki-in-11 technique, 1. When the insulation 1- and the conductive or resistive pattern are simultaneously fired, the glass frits in both pastes melt into each other, and the resistance value of the resulting conductor is not constant. 21i firing was required.

(Objective of the invention) In the present invention, in order to eliminate or compensate for the above-mentioned defects, it is possible to bake once at 700 to 900C,
The present invention provides a method for manufacturing a planar heating element that has excellent infrared radiation characteristics and is inexpensive and easy to process.

(Structure of the Invention) That is, the present invention provides a conductive resistance base (Ii') by interposing an insulating coating layer mainly composed of crystallized glass on a ceramic green sheet made using papermaking technology. This is a method for producing a planar heating element characterized by integral firing at a low temperature of about 700 to 900C.

(Function of the Invention) According to the present invention, a method for manufacturing a planar heating element in which a crystallized glass @ is interposed between a substrate that can be sintered at low temperature but whose surface tends to be porous and a conductive resistor paste. In the case of crystallized glass f-, partial crystallization occurs at a temperature lower than the firing temperature of 700 to 900 C, forming a dense intermediate layer. In addition, crystallization 1. The intermediate I- of the glass has a property that it is difficult to mix with the upper conductive resistance layer during firing and when electricity is applied, and the conductive resistance layer does not penetrate into the porous substrate and melts with the crystallized glass layer. will no longer match.

(In the detailed description of the invention, the ceramic green sheet is 700 to 90%
The thermal expansion coefficient is 30 to 40X10- so that it can be fired at 0C, and so that the fired substrate will not crack due to thermal shock.
' Select and mix raw materials to achieve a ratio of about 1/C. The fibers are coagulated in water and made into paper 12 and sheets. This sheet is heated and dehydrated and pressed at 5 to 15 MPa and 110 C to produce a ceramic green sheet toner.

An example of blending an inorganic material to obtain a sintered substrate having such low temperature sinterability and a low coefficient of thermal expansion will be described. As an example, a commonly used ceramic raw material is used, and the raw material composition is cordierite composition (2Mg0, 2t2
0.・55i02) The proportions of alumina, silica, and magnesia may be adjusted so as to approximate it.

To explain this point more specifically, commonly used ceramic raw materials, such as frog's eye clay.

Akatsuki talc, kaolin, etc. are pure At206.5iOz
, does not consist of MgO, but also contains water (H2O)
In addition to alkali gold@oxides (Na2O, Ni20, etc.), alkaline earth metal oxides (CaO, etc.), and iron oxides (Fe20B, etc.) as residual iron, which are impurities that can be subjected to IIJE in a stoichiometric formula. These H2O
, Na2O, Fe2O3, etc., have the disadvantage of increasing the coefficient of thermal expansion, but on the other hand, even a small amount of impurities may lower the sintering temperature. In the present invention, the weight ratio of these impurities is kept within the range of 3 to 12%, and the blending ratio of the main components At205, SiO2, and mO is blended as raw materials so as to have a cordierite composition. By doing this, it is possible to perform sintering at a low firing temperature, and at the same time, it is possible to obtain a sintered substrate with a low coefficient of thermal expansion.

For reference, the weight percentages of Nb2O2, SiO□, and MgO, which are the main components, of four types of commonly used ceramic raw materials are shown. The remainder corresponds to the above impurity.

If we use ordinary ceramic raw materials as mentioned above.

The MgO component is lacking, and in order to bring the main component closer to the cordierite composition, it is added from outside MgOk, depending on the selection of raw materials used.

In addition to the above-mentioned formulation examples, an inorganic material with low melting sinterability can be obtained by adding a glass 71J as a flux to the raw material composition with high temperature sinterability.

In any case, a coating composition is prepared by kneading a green sheet obtained using a paper-making technique with an organic solvent such as terpineol, which is a crystallized glass frit. It is applied by means such as printing or coating to provide an insulating coating layer. The pattern to be applied may be a solid coating on the surface of the green sheet or may be a pattern that matches the pattern of the conductive paste layer.

After drying this insulating coating layer, a desired resistance value is obtained by using a conductive resistive paste containing metal chromium, ruthenium oxide (Ru02), etc. as the main component, or by screen printing or other means. Do you get a comb-like or striped resistance pattern? create.

This printed green sheet is burnt and vaporized in the middle of fibrous and organic matter in an electric furnace in an oxidizing atmosphere. Thereafter, heating is continued to sinter the substrate and the resistor paste donor together at about 800C. In this way, a planar heating element is produced.

In the present invention, the paste used for absolute *+*i is made of crystallized glass, and during firing, there is little interaction with the frit in the upper layer of resistance paste, and the heat generation that has a constant resistance value is low. Compare the resistor obtained. And is this 111- the pores on the substrate surface during firing? In order to seal the hole, an inexpensive planar heating element can be obtained by firing at a low temperature of about 800C.

Specific examples of the present invention will be described below. All compositions are by weight.

<Example 1> [F]) Flocculant (Q Insulating coating composition Insulating paste (460B-N Hakuto #) 04 Resistance paste Cr paste (Hakuto, Construction, #2560) First, put it in a 2I3ffllt container. Water 1. o o
Add o parts and 10 parts of wood pulp, stir for 20 minutes,
Thoroughly disperse and beat in pulpy water and add 18%
Add 0 parts and 20 parts of magnesium oxide and stir for 1 minute to form an aqueous slurry. make.

Add 60 parts of aluminum sulfate prepared in advance to this aqueous slurry and stir until the pH reaches 3 using pH test paper.
~Did it become 4? Check this and add the polyacrylamide polymer flocculant 120 that you made in advance.
Add 50% of the mixture and stir for 30 seconds to coagulate. The agglomerated sample as described above is made into a paper using a paper making machine to form a sheet having a thickness of 1.5 to 2.2 mm by 300 mm. Using this sheet press, the material is dehydrated and dried under a pressure of 10 MPa at 110C to produce a green ceramic sheet.

On this green sheet, an insulating paste of 30 to 50 μm is formed using an insulating paste made of crystallized glass.

Cr paste on this green sheet v resistance after firing is 50
Print in a tooth shape with screen printing so that the resistance is ~100Ω.

The green sheet printed with the resistance paste is fired in an oxygen atmosphere in an electric furnace.

For firing, the temperature was raised from room temperature to 4000C at a rate of 2tZ'/min, held at 400C for 1 hour, and the organic binder,
pulp? Burn and vaporize. That ff1. ao.

The temperature was raised to C at 4 C/min, held at 800 C for 30 minutes to sinter the ceramics and fire the paste, and then allowed to cool in the furnace to room temperature to produce a sheet heating element.

<Example 2> (Sample preparation IBI flocculant and surfactant (0 conductive resistance paste C "Paste" (Hakuto ■ Seki, #: 25 (50).

Using the above compositions fA), FB+, and (0), the following procedure was performed in the same manner as in Example 1 to measure sheet heating of ceramics.

I got a body.

(Effect of the invention) The sheet heating element thus obtained has a stable resistance value of the conductive resistance layer, and can be used in fields such as home saunas, kotatsu, heaters, etc., as well as medical and food industry machines. It has excellent high temperature resistance and durability.

According to the present invention, a planar heating element of any shape can be manufactured due to its thinness and good workability, and has the advantage of being able to withstand high temperatures compared to conventional plastic planar heating elements.

In addition, compared to conventional ceramic planar heating elements, it can be fired in one step at a lower temperature, which simplifies the process, has excellent thermal shock resistance, helps with overwriting energy, and can be supplied at low cost. It is a.

Claims (1)

[Claims] (1) A conductive resistive paste layer is provided on a ceramic green sheet made using papermaking technology with an insulating coating layer mainly composed of crystallized glass.
A method for manufacturing a planar heating element, characterized by integral firing at a low temperature of about 0 to 900°C.